The arrangement of three double sensors around the rotary axis of a rotating body, for example a drive shaft of a turbine, is known in the prior art. The rotational direction is determined by means of an evaluation unit using the sensor signal from the two sensors of a double sensor, in particular making use of the flank patterns. The three rotational directions are then compared to one another in an evaluation unit, and when two rotational directions accord with one another these are output as the correct rotational direction. The use of this rule, known as “2 out of 3”, is important when safety and availability requirements are high. If one of the sensors fails, two double sensors remain, on the basis of which the rotational direction can still be redundantly determined. Due to the high safety requirements of power station construction, redundancy is necessary. However, the use of three double sensors is on the one hand expensive, due to the use of a total of six sensors, while on the other hand, due to the amount of room available for installation, problems are involved in the arrangement of these relatively high-volume sensors.